Conversion of pig iron into steel

ABSTRACT

A refining process for converting pig iron into steel wherein at least one tuyere is mounted in the side wall on the converter and the tuyere has an inner conduit and an outer conduit. Substantially pure oxygen is injected through the inner conduit and a protective fluid is injected through the outer conduit. The axis of the tuyere is inclined towards the bottom of the converter so that the injected oxygen creates rotational movement in the molten metal so as to better distribute the oxygen throughout the melt and control the decarbonization of the converter. The tuyere in the side wall is mounted at the level of the zone occupied by the slag.

United States Patent 11 1 Nilles 1451 Aug. 19, 1975 1 CONVERSION OF PIGIRON INTO STEEL [75] Inventor: Paul Emile Nilles, Embourg Belgium [22]Filed: Nov. 3, 1972 [21] Appl. No: 303,357

3.079249 2/1963 Moustier 75 60 3,330,645 7/1967 M0ustier..... 75/605,556,773 1/1971 Grenfell 75/52 3706549 12/1972 Knuppel 75/60 PrimaryEtuminerL. Dewayne Rutledge Assistant ExaminerPeter D. RosenbergAttorney, Agent, or Firm-Holman & Stern 5 7 ABSTRACT A refining processfor converting pig iron into steel wherein at least one tuyere ismounted in the side wall on the converter and the tuyere has an innerconduit and an outer conduit. Substantially pure oxygen is injectedthrough the inner conduit and a protective fluid is injected through theouter conduit. The axis of the tuyere is inclined towards the bottom ofthe converter so that the injected oxygen creates rotational movement inthe molten metal so as to better distribute the oxygen throughout themelt and control the decarbonization of the converter. The tuyere in theside wall is mounted at the level of the zone occupied by the slag.

6 Claims, 3 Drawing Figures CONVERSION OF PIG IRON INTO STEEL BACKGROUNDOF THE INVENTION The present invention relates to a refining process forthe conversion of pig iron into steel.

It is known that the problem of the life of the bottom of anoxygen-blown converter has been solved by the use. for the injection ofindustrially pure oxygen beneath the surface of the metallic bath, oftuyeres comprising two concentric conduits located either in the bottomor in the side wall beneath the surface of the metallic bath, thecentral conduit serving for the blowing-in of pure oxygen, theperipheral conduit serving SUMMARY OF THE INVENTION The presentinvention provides a refining process in which, by means of one or moretuyeres comprising two coaxial tubes and located in the wall ofaconverter, above the upper level of the hot metal, technically pureoxygen is injected into the metal bath through the central tube of thetuyeres and then a liquid and/or gaseous protective fluid is injectedthrough the peripheral conduit of the tuyeres, the tuyeres beinginclined towards the bottom of the converter.

The oxygen and the protective fluid may advantageously be injectedthrough one or more such tuyeres in the wall of the converter at thelevel of the zone occupied by the slag, which enables the appearance ofthe reactive character of the slag to be accelerated.

Owing to the possibility of placing the oxygen directly in contact withthe slag and metal, the present process has the important advantage ofallowing an easy distribution of the oxygen between the metal and theslag and consequently the control of thc dccarburization rate;furthermore, inclination of the tuyere enables wear of the refractoriesin the side wall opposite the tuyere to be avoided.

It has been confirmed that with the present process it is also possibleto avoid the formation of metallic heads on the periphery of the tuyereswithin the converter; such heads constitute a handicap to the processesin which the injection of oxygen is made beneath the surface of the hotmetal.

The diameter of the tuyere as well as the rate of flow of oxygen andprotective fluid are preferably arranged to he adjustable andcontrollable, in order to accelerate the refining of the pig iron.particularly by helping to rapidly form a fluid reactive slag.

Each injection may advantageously be effected along an axis inclinedtowards the bottom of the converter and located in a diametrical planeof the converter, which results in producing in the metal a doublerotational movement at one and the same time in a vertical plane and ina horizontal plane. which produces excellent mixing of the hot metal andthorough decarburization.

The injection can be carried out by means of a single tuyere, directedtowards the bottom of the converter, the direction of the jet of oxygennot however passing through the axis of the converter.

The injection may be carried out simultaneously on different levels,namely above the level of the slag and into the slag, their directionnot passing through the longitudinal axis of the converter. Byjudiciously selecting the speeds and rates of flow to the differentinjection tuyeres, a differential rotational movement between the metaland the slag is achieved, which enables the physico-chemical exchangesat the slag/metal interface to be increased, and therefore acceleratesdecarburization.

The rotational movements imparted to the slag and metal are judiciouslycontrolled by the arrangement of the tuyeres in the wall of theconverter. For this purpose, according to requirements, the tuyeres canbe arranged to be orientated in the same sense in relation to the axisof the converter or in the opposed sense, whether side by side orspaced, in the wall of the converter all around its periphery.

It is within the scope of the present invention to place one or severalpulvcrulent materials, preferably slagging materials, such as forexample lime, in suspension in the oxygen.

The protective fluid is advantageously composed of a gaseous or liquidhydrocarbon.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a vertical cross-section ofa converter according to the instant invention; and

FIGS. 2 and 3 are simplified [horizontal cross-sections of the outsidewall of the converter showing two embodiments of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS According to FIG. I, tuyere 1has an inner tube 2 for the blowing of oxygen and this tube 2 issurrounded by a concentric tube 3 through which a cooling medium isinjected. This tuyere I is inserted in a side wall 4 of a converter 5and the longitudinal axis 6 of this tuyere l is inclined towards theconverter bottom with the jet of oxygen directly impinging on slag 7,molten metal 8 being underneath.

The angle of inclination of the tuyere is a and is the angle made by thelongitudinal axis 6 of the tuyere with a horizontal plane 9 passingthrough a point 10 where this lontitudinal axis 6 enters the converter,when the converter is stationary with its longitudinal axis 12 invertical position.

FIG. 2 shows the tuyere I with its longitudinal axis 6 inclined towardsthe bottom of the converter and located in the diametrical plane of theconverter. Such a location results in producing in the metal a doublerotational movement (arrows l3 and I4) at one and the same time. Thismovement also takes place in a vertical plane and in a horizontal planebecause of the inclination a of the tuyere towards the metallic bath.The jet of oxygen with cooling medium impinges the molten metal andproduces two force components: one vertical (arrow 15. FIG. I) and onehorizontal (arrow I6, FIG. 1).

FIG. 3 shows the tuyere I having a longitudinal axis 6 which does notintersect longitudinal axis I2 of the converter. The direction of thisaxis 6 many he defined by a distance 17 between axis 6 and axis 12. Sucha direction enables a rotational movement (arrow 18) in the metal and inthe slag to be achieved. In the case of several tuyeres located atdifferent levels, a differential rotational movement between the metaland the slag may be achieved by judiciously selecting the speeds andrates of flow to different injection tuyercs.

I claim:

1. A refining process for the conversion of pig iron into steel in aconverter wherein the molten metal is ag itated by blown oxygen so as tobetter distribute the oxygen throughout the melt and control thedecarburization, the converter having a bottom, a side wall, and atleast one tuyere in the side wall, the tuyere comprising an innerconduit and an outer conduit surrounding the inner conduit, the processincluding the steps of injecting substantially pure oxygen through saidinner conduit onto the molten metal in the converter, and in jecting aprotective fluid through the outer conduit, the tuyere opening into theconverter through the sidewall at the level of the zone occupied by slagand the axis of the tuyere being inclined towards the converter bottomto create rotational movement of the molten metal.

2. A process as claimed in claim 1, in which the axis of the tuyere isdirected along a line contained in a diametrical plane of the converter.

3. A process as claimed in claim 1, in which only one tuyere is used,the axis of the tuyere being directed towards the converter bottom alonga line which does not intersect the converter axis.

4. A process as claimed in claim 1, in which two tuyeres are used, oneopening into the converter above the slag layer and the other openinginto the slag layer, the axis of each tuyere being directed along a linewhich does not inersect the axis of rotation of the converter, the speedand flow rate of the materials injected through the tuyere being suchthat the molten metal and the slag rotate at different speeds.

5. The process as claimed in claim 1, in which pow dery material is insuspension in the injected oxygen.

6. The process as claimed in claim 1, in which the protective fluid is ahydrocarbon.

1. A REFINING PROCESS FOR THE CONVERSION OF PIG IRON INTO STEEL IN ACONVERTER WHEREIN THE MOLTEN METAL IS AGITATED BY BLOWN OXYGEN SO AS TOBETTER DISTRIBUTE THE OXYGEN THROUGHOUT THE MELT AND CONTROL THEDECARBURIZATION, THE CONVERTER HAVING A BOTTOM, A SIDE WALL, AND ATLEAST ONE TUYERE IN THE SIDE WALL, THE TUYERE COMPRISING AN INNERCONDUIT AND AN OUTER CONDUIT SURR OR INJECTING SUBSTANTIALLY PURE OXYGENTHROUGH SAID INNER CONDUIT ONTO THE MOLTEN METAL IN THE CONVERTER, ANDINJECTING A PROTECTIVE FLUID THROUGH THE OUTER CONDUIT, TE TUYEREOPENING INTO THE CONVERTER THROUGH THE SIDEWALL AT THE LEVEL OF THE ZONEOCCUPIED BY SLAG AN THE AXIS OF THE TUYERE BEING INCLINED TOWARDS THECONVERTER BOTTOM TO CREATE ROTATIONAL MOVEMENT OF THE MOLTEN METAL.
 2. Aprocess as claimed in claim 1, in which the axis of the tuyere isdirected along a line contained in a diametrical plane of the converter.3. A process as claimed in claim 1, in which only one tuyere is used,the axis of the tuyere being directed towards the converter bottom alonga line which does not intersect the converter axis.
 4. A process asclaimed in claim 1, in which two tuyeres are used, one opening into theconverter above the slag layer and the other opening into the slaglayer, the axis of each tuyere being directed along a line which doesnot inersect the axis of rotation of the converter, the speed and flowrate of the materials injected through the tuyere being such that themolten metal and the slag rotate at different speeds.
 5. The process asclaimed in claim 1, in which powdery material is in suspension in theinjected oxygen.
 6. The process as claimed in claim 1, in which theprotective fluid is a hydrocarbon.